The present invention relates to a solenoid control valve for a gas direct injection fuel injector and more particularly to a dual coil, high force solenoid control valve for a gas direct injection fuel injector.
Solenoid-actuated valve assemblies are widely used in a variety of applications including fuel injection systems. Typically the solenoid valve assembly has a housing within which is disposed a solenoid and a valve in axial alignment with one another. The solenoid typically includes a coil, a stator, a movable armature and a valve. Upon energization and de-energization of the coil, the armature moves to open and close the valve. It is desirable to have the injector as small as possible in order to fit within the limited space surrounding each cylinder of an engine. For example, direct injection fuel injectors typically have an outside diameter of 22 mm or larger.
Single coil solenoids are typical in fuel injection systems. However, they are often bulky and require high current and voltages in order to achieve the high force required to control the fuel flow requirements for the direct injection engine.
Dual coil solenoid devices also are typical in fuel injection engine systems. Typically, the coils are energized independently. For example, a first coil is energized to open the valve and a second coil is energized to close the valve. In other assemblies, the coils are energized simultaneously, but also independently, for a limited period of time. A first coil, having a high current, is used as a pull coil. The second coil, having a low current is used as a hold coil. In this example, a timing circuit is necessary in order to switch off the pull coil after the predetermined period of time has lapsed.
The problem with most dual-coil solenoid assemblies is that two separate drivers are needed to energize the coils. This adds size, weight, and obviously, cost to the solenoid assembly. In assemblies where the coils are energized simultaneously, high current drivers are required in order to achieve the necessary forces. Also, much larger diameter injectors, with high voltage, are required. These features also add unnecessary cost and complexity to the solenoid assembly.
Another concern is the fact that most engines have a wire harness plug to join the engine""s circuitry to the solenoid assembly. The typical OEM wire harness plug provides a fixed electrical configuration, usually two or three electrical contacts, for supply to the solenoid. In some circumstances, dual-coil solenoid arrangements are not compatible with the standard OEM wire harness plug, which makes retrofitting solenoid assemblies costly and otherwise impractical.
The present invention is a dual coil, high force, solenoid valve for a gas direct injection fuel injector. The solenoid has two low inductance coils connected in parallel and simultaneously energized. The coils are wound in opposite directions such that the magnetic field created between the coils in a shared air gap is additive and creates a high flux density air gap, thereby creating a high force. Because the coils are connected in parallel, they create a very low inductive load to the injector driver. Lower inductive loads for the injector driver create faster current rise and fall times, which in conjunction with the high force, create very fast injector response times.
The invention is directed to the actuator, or solenoid, portion of an injector. A body houses two low impedance, low inductance coils connected in parallel, and wound in opposite directions. An armature, having three air gap surfaces with the body and a plug, is movable within the body. One of the air gap surfaces is mutually shared between the two coils and because of the opposing directions of the coil windings, the magnetic force is additive between the coils. Thus, the force generated in the mutually shared air gap has a high flux density and therefore produces a high force.
It is an object of the present invention to improve the response of a direct injection fuel injector. It is another object of the present invention to provide a high force for a direct injection fuel injector. It is still another object of the present invention to produce high magnetic forces with less current than conventional fuel injector solenoids.
It is a further object of the present invention to produce high magnetic forces within a packaging space that is smaller than conventional solenoids. Still a further object of the present invention is to provide a dual coil, high force solenoid having two coils connected in parallel and wound in opposite directions such that an additive magnetic force is created in an air gap surface that is mutually shared between the two coils.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.